The Province of Zamboanga del Sur is a small piece in the bigger and former Spanish colonial era Zamboanga province. The latter originally encompassed the whole of the present-day Zamboanga Peninsula Region and the provinces of Basilan, Sulu, and Tawi-Tawi.

Pursuant to the provisions of Act No. 83 or The Provincial Government Act of 1901, the Philippine Commission implemented a national political reorganization. In accordance with Act No. 787 approved on June 1, 1903 and made effective on July 15, 1903, the Moro Province was created out of Mindanao. It excluded provinces of Surigao and Misamis which were previously created under Act No. 127 and Act No. 128, respectively. It set the Municipality of Zamboanga as its capital (section 1).

Under Section 2.b of Act No. 787, the Zamboanga District also hadas its territory the Island of Basilan and its immediately adjacent islands not included in the Sulu District.

Enacted on July 23, 1914 and took effect on September 1, 1914, Act No. 2408 renamed Moro Province as the Department of Mindanao and Sulu. The Municipality of Zamboanga was still the capital (para. 2, Section 2, Article I, Chapter I).

The Province of Zamboanga del Sur was composed of the municipalities of Molave, Aurora, Labangan, Pagadian, Dimataling, Margosatubig, Ipil, Kabasalan, Dinas, Molangas and Alicia (Section 1). Pagadian was named as the capital (Section 2).

Under Section 7 of RA 711, “the cities of Basilan and Zamboanga shall form part of the representative district of Zamboanga del Sur”.

RA 711 authorized the President of the Philippines,with the consent of the Commission on Appointments, to appoint the governor and members of the provincial board. Atty. Serapio Datoc was appointed as the provincial governor. He was also the last governor of the undivided Province of Zamboanga.

On November 7, 2000, President Joseph Estrada signed into law the Republic Act No. 8973, which created the Province of Zamboanga Sibugay out of the Province of Zamboanga del Sur. The municipalities of Buug, Diplahan, Malangas, Imelda, Alicia, Mabuhay, Olutanga, Talusan, Payao, Siay, Kabasalan, Naga, Ipil, Titay, Roseller T. Lim and Tungawan comprised the new province (Section 2).